2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
org 100h

;write prompt
mov ah, 09h
mov dx, prompt
int 21h

;read input
mov ah, 0Ah
mov dx, buffer
int 21h

;s7 - (s1 - s2)
mov ah, [buffer + 2]
sub ah, [buffer + 3]

mov al, [buffer + 8]
sub al, ah
mov [buffer + 5], al

;swap s5 and s8
mov ah, [buffer + 9]
mov al, [buffer + 6]

mov [buffer + 9], al
mov [buffer + 6], ah

;output result
mov ah, 09h

mov dx, newline
int 21h

mov [buffer + 10], '$'
mov dx, buffer + 2
int 21h

ret

buffer db 9, 0, 9 dup(?)
newline db 13, 10, '$'
prompt db 'Enter line of 8 characters: ', 10, 13, '$'